A severality of stair-climbing wheel chairs have been described and detailed in the art. For example in U.S. Pat. No. 3,104,112, issued Sept. 17, 1963, to J. W. Crail, a device is disclosed in which an occupant-propelled folding wheel chair is provided with a folding frame upon which is mounted a pair of front casters and a pair of rear main wheels sufficiently large in diameter to roll over normal stair steps. The chair is adapted for occupant propulsion by hand-operated means for driving said main wheels.
A stair climbing mechanism is provided which includes a pair of arms, one carried on each of the side frames. The arms are pivoted at the rearward end coaxially with one of the main wheels. This permits the forward end of the side arm to swing between a raised and lowered position. Further, a pair of stair climbing wheels, one mounted forward of each of the arms, is provided which has a diameter smaller than the main wheel but large enough to roll over normal stair steps. Additionally, a transverse brace member is disposed between the arms sufficiently forward to clear the side frames of the chair during the swinging movement of the arms. In addition, a linkage means on each of the side frames is pivotally mounted on the side frames. The linkage means are adapted to be manually operated by an occupant of the wheel chair to move the arms from a raised to a lowered position for stair climbing. A ratchet gear integrally rotatable with each of the main wheels, together with retractable pawl means for engaging the ratchet gear during stair climbing, is provided. Also, a releasable latch means for holding the stair-climbing position of the elements is provided.
In U.S. Pat. No. 3,169,596, issued Feb. 16, 1965, to S. A. Wright, a step traversing wheel chair is disclosed comprising the combination of a chase with wheels for traveling over even surfaces. Additionally, one or more rotatable screws transversly spaced and disposed in rearwardly inclined positions and connected to the chase are provided for propelling the same over steps. Means for rotating the screws and means for raising and lowering the wheels whereby the screws may assume a step engaging position when the wheels are retracted are also provided.
In U.S. Pat. No. 3,226,128, issued Dec. 28, 1965, to R. C. Brier, Jr., a wheel chair is described having a frame and seat supported by a pair of spaced wheel assemblies with hubs carried by shafts. Means for ascending and descending a stairway include support means positioned forwardly of the frame which are adjustable to the angle of the stairway to be traversed. Further, a plurality of gripping means are spaced circumferentially about the hub of the wheel chair and extending radially beyond the wheels of the chair while ascending a stairway. The plurality of gripping means rotate rearwardly responsive to an upward and rearward force being applied successively to forwardly extending gripping means by the occupant of the chair. This causes the rearwardly extending gripping means to successively contact the steps and lift the chair up as the occupant pulls upward and rearward. In addition, a locking means is provided which permits the chair to slide down the stairway when a gripping means is released prior to engaging the next gripping means. Additionally, a means for limiting forward movement of the gripping means is required when descending the stairway in predetermined increments of movement.
In U.S. Pat. No. 3,304,094, issued Feb. 14, 1967, to R. B. Wenger, a wheel chair is described comprising a seat frame having depending rear supporting leg means and depending front supporting leg means which support wheels connected to the seat frame at its opposite sides. Respective elliptical wheels slidably and pivotally connected to the opposite sides of the seat frame at the rear portion thereof are arranged in vertical longitudinal planes and means are provided to rotate the elliptical wheels into engagement with a rearwardly adjacent stair step. This causes the elevation of the rear portion of the seat frame. Respective caster assemblies, slidably connected to the front supporting leg means at the opposite side of the seat frame are provided with means to extend the caster assemblies downwardly when needed so that the seat frame may be leveled when the rear portion thereof is raised or lowered.
Many handicapped persons are weak or so infirmed as to lose much of their dexterity and in some instances possess voluntary motor response in only one or two fingers or less. Further, many individuals confined to wheel chairs are extremely susceptible to blows or impact and find it unwise to hazard precarious disorientation or loss of traction of a vehicle proximate a stairway which occurrence could result in an accident. More specifically, the machines of U.S. Pat. Nos. 3,104,112 and 3,226,138 and 3,304,904 are manually propelled and require great strength to operate. Further, the chair of U.S. Pat. No. 3,104,112 is suitable for the ascent of stairs but has no provision for descent, and the machine of U.S. Pat. No. 3,304,094 provides means for ascending or descending stairs with the rearward portion of the chair and leveling the attitude of the chair by extending or retracting the forward wheels, but no provision is made for traversing stairs with the forward portion of the chair. Also, the chairs of U.S. Pat. Nos. 3,104,112 and 3,304,904 depend upon the coefficient of friction of a curved surface located at an angle to the stair during the traversing of such stairs to prevent accidental slippage and possible accident. Still further, the chairs of U.S. Pat. Nos. 3,169,596 and 3,226,128 require great dexterity or balance to commence or conclude the stair traversing mode. Furthermore, the operation of the stair climbing apparatus of U.S. Pat. No. 3,169,596 may cause damage by friction to stair faces and, should the pitch of the stair tread not coincide with the pitch of the screw member, the screw member may be prevented from engaging the stair tread by interference between the periphery of the helical member and the nosing of a stair tread.
Further, wheelchairs which accomplish stair traversal using rotated endless belts or tracks combined with cleats thereon for supportively contacting a stair tread have been described and detailed in the art. For example, the Letters U.S. Pat. No. 3,529,688, issued on Sept. 22, 1970, to John W. Bruce. However, such chairs are often unsafe given that step size of various stairs will undoubtedly vary, and as the belts or tracks traverse from stair tread to stair tread, the selectively spaced cleats may or may not mate with each successive stair tread. Thus, where a cleat does not precisely mate with the next stair tread encountered, the cair must slip downwardly since load is transferred from one cleat to a second cleat. This problem is discussed with regards to stair-climbing wheelchairs in VAREC REVIEW, Vol. 1, No. 2, May 1981 (Veterans Administration Rehabilitation Engineering Center, 252 Seventh Avenue, New York, N.Y. 10001).
Accordingly, it is an object of the present invention to provide a wheel chair suitable for rolling or being propelled across flat and inclined surfaces on wheels and suitable also for traversing steps. Another object of the present invention is to provide a wheel chair having means for traversing steps which provides positive traction by firmly gripping the surfaces of the treads. Yet another object of the present invention is to provide a wheel chair having driven lugged chains suitable for contacting a step and propelling a wheel chair traversing said step. Still another object of the present invention is to provide a deployable lug for the driven chain of the chair which increases the grasp of the stair tread during ascent and descent. An additional object of the present invention is to provide a wheel chair for traversing steps with means to automatically maintain the occupant properly balanced in the chair.
Still another object is to provide a wheel chair which is adaptable for movement over substantially level terrain as well as along stairs which may be manually operated safely with a minimum effort by an occupant. A further object is to provide a motor driven wheel chair for use in ascending and descending stairs with means for orienting and then maintaining the wheel chair movement perpendicular to stair treads.
It is a further object of the present invention to provide a wheel chair which is not subject to downward slippage as the chair traverses a stair and load is shifted from one stair tread to another.
Furthermore, it is an object to provide apparatus for moving objects up and down stairways while maintaining the objects in a stable altitude. Other objects and advantages of the invention will become apparent upon reading the detailed description and referring to the drawings.